Diabetic retinopathy is a devastating ocular manifestation of diabetes mellitus and is a major cause of blindness in the United States. The morphological hallmark of this disorder is microvascular basement (MB) disease, a progressive thickening of the BM surrounding capillaries. In an effort to elucidate the pathogenesis of the altered BM's in this condition, we propose and in-depth analysis of isolated retinal vessel BM from normal and diabetic animal models or patients. Pure preparations of dissociated retinal vessels from bovine and normal and diabetic monkey and human eyes will be used in this study. From these vessels we will isolate ultrastructurally pure BM that: a) is morphologically defined; b) is tissue specific; and c) can be isolated in quantities adequate for biochemical analysis. Isolated retinal vessels are readily cultured and produce BM which can be directly compared to those isolated in vivo. Moreover, morphological and biochemical analyses can be correlated with clinical observations. In the proposed study we will analyze retinal vessel BM in vivo and newly synthesized BM in vitro by: a) experimental ultrastructural techniques to study species, tissue and local dissimilarities in BM substructure; b) biochemical identification of collagen types; and c) immunohistochemical localization studies of noncollagenous glycoproteins (i.e. fibronectin, laminin). In addition, we propose in vitro biosynthesis studies which will be controlled by nutritional or hormonal factors (e.g., glucose, insulin) to induce changes that may simulate those observed in diabetics in vivo. Wherever possible, analyses will be correlated with clinical observations. It is hoped that these studies will provide insights into the nature of BM alterations in diabetes. We believe that when these are clarified and the parameters surrounding the pathogenesis of the disorder are more fully understood, the possibility of elucidating its causes will be within reach. This could lead ultimately to positive therapeutic intervention in the progression of diabetic BM disease.